222 Notes

Cell Cycle: Sequence of growth and division in cells, organized in a spatiotemporal manner; involves phases such as mitosis and differentiation.
Terminal Differentiation: Fully mature cells that have specific functions and exit the cell cycle, though some can undergo redifferentiation in response to environmental stimuli.
Cell Types:
- Differentiating Cells: Start to form a central vacuole.
- Expanding Cells: Vacuoles coalesce, leading to growth.
- Meristematic Cells: Small cytoplasm, no central vacuole, undifferentiated, crucial for plant growth.
Cell Synchronization: Differentiation processes in plants are not synchronized.

Morphology: The shape and structure of plant components.
Key Structures:
- Terminal Bud: Shoot apex at the end of the stem.
- Blade: Outer leaf structure.
- Axillary/Lateral Bud: Buds growing from the stem node where the leaf connects.
- Primary Root: Vertical main root with lateral roots and offshoots.
Main Differences between Plant and Animal Cells:
- Plant cells possess cell walls, central vacuoles, and chloroplasts.
- Cytoplasm: Aqueous liquid containing organelles, differentiation between cytosol (liquid portion) and protoplast (includes plasma membrane and everything inside it).
- Apoplast: Refers to everything outside the plasma membrane including the cell wall.

Cell Wall Functions:
- Maintains cell shape, protects, and controls turgor pressure.
Microfibril Orientation: Determines cell shape; can expand isotropically (circular) or anisotropically (rectangular).
Composition:
- Cellulose: Polysaccharide forming microfibrils providing strength.
- Hemicellulose: Cross-links cellulose molecules, enhancing strength.
- Pectin: Provides flexibility due to gel-like properties.
Types of Cell Walls:
- Primary Cell Wall: First formed in all cells, thin and flexible.
- Secondary Cell Wall: Formed later in some cells, thicker and more rigid, with high lignin content for added support.

Process of Cell Wall Formation:
1. New walls form during mitosis, particularly cytokinesis,
2. Cell plate expands outwards and fuses with the parental wall.
3. Cellulose microfibrils are synthesized by enzymes in the plasma membrane, guided by microtubule orientation.

Function: Allows intracellular movement of small molecules like proteins and RNA, essential for cellular communication.
Structure: Contains a desmotubule surrounded by endoplasmic reticulum.
Primary Pit Fields: Locations densely populated with plasmodesmata in primary walls.

Tissue Types:
- Dermal Tissue: Protects plant and controls movement in/out, has a waxy cuticle.
- Vascular Tissue: Xylem for water/mineral transport; phloem for sugar transport.
- Ground Tissue: Fills space between dermal and vascular systems.
Meristem Tissues: Regions for cell division, leading to growth (primary and secondary meristems).

Xylem: Transports water/minerals; composed of tracheary elements (tracheids and vessel elements) and supports through fibers.
Phloem: Transports sugars and nutrients; includes sieve elements (sieve tube elements and companion cells).

Meristems: Sites for active growth; apical meristem at shoot and root tips, lateral meristem for thickness (vascular cambium and cork cambium).
Growth Zones: Central zone for organization, peripheral zone for organ primordia.

Formation characterized by seasonal variations; earlywood is lighter and larger cells, while latewood is denser and smaller.
Cork Cambium: Forms protective layers in the bark of woody plants.

Lenticels: Small openings in the periderm allowing gas exchange.
Periderm: Formed from cork cambium, providing protection and preventing water loss.

Identification of key parts: terminal bud, vascular cambium, axillary buds, leaf scars, and growth rings (both primary and secondary).
Life Cycle and Tissues: Secondary phloem remains functional, while older phloem becomes non-functional and filled with waste.